The top-seeded Roger Federer made it to the semi-finals of the Halle Open with a 6-0, 7-6 victory over Germany's Florian Mayer on Friday.
Next off for Federer will be Ivo Karlovic, a winner against Tomas Berdych earlier in the day.
Federer said he intends to put pressure on Karlovic's serve when they meet.
"Well I think it starts with focusing on your own game and your own serve, you know. Then you take it from there, clearly I'm going to try and have as big an impact on his second serve, try to pressure his first serve and then when it gets important, you know, maybe he gets a little bit nervous, maybe you can play your best tennis when it really matters."
No. 2 Kei Nishikori got a win over Jerzy Janowicz of Poland 6-4, 5-7, 6-3.
Italian Andreas Seppi also advanced after fourth seed Gael Monfils pulled out of their match with a right knee injury.
